There is a part in the file cortex.h that is as follows:
/* minimal implemented priority required by Cortex core */
#define CORTEX_PRIOR_IMPL (1)
#define CORTEX_PRIOR_IMPL (3)
#endif /* CORTEX_PRIOR_IMPL */
The CORTEX_PRIOR_IMPL value is used to set the value of the priority levels in nvic.c (line 58, fcn _nvic_int_init), and that definition is saying that for Cortex M4 the CORTEX_PRIOR_IMPL is 3 but that seems to be wrong. Reading on the reference manual for the MCU family I'm using it says that it supports up to 16 priority levels. Having that definition as 3 limits the priority levels to 8 and that is just half of what we would have available.
I don't remember having read anything about cortex.h being a file that can be configured by the user but if I change that 3 for a 4 then I have all 16 priority levels available.
It seems like that value as 3 could be the correct value for some families with less than 16 priority levels and that for other families like the one I'm using it can be configured as 4, but I'm not sure.
Is this a bug or something that is supposed to be that way? Could someone please confirm this?